+=head2 Hash2grs
+
+This method converts a hash into a GRS-1 object. Scalar entries within the hash are converted
+into GRS-1 string elements. A hash entry can itself be a reference to another hash. In this case,
+the new referenced hash will be converted into a GRS-1 subtree. The method is called this way,
+
+ $grs1->Hash2grs($href, $mapping);
+
+where $href is the hash to be converted and $mapping is referenced hash specifying the mapping
+between keys in $href and (type, value) pairs in the $grs1 object. The $mapping hash could
+for instance look like this,
+
+ my $mapping = {
+ title => [2, 1],
+ author => [1, 1],
+ issn => [3, 1]
+ };
+
+If the $grs1 object contains data prior to the invocation of Hash2grs, the new data represented
+by the hash is simply added.
+
+